A piston for an internal combustion engine is known from DE 10 2010 018 930 A1. This piston comprises four valve pockets within the piston crown, which ensure clearance for the exhaust valves and inlet valves.
With an Otto gas engine, pistons with different piston recess shapes are used. As a rule, a distinction is made between the following common variants:
A) Piston with roof-shaped piston crown. The piston crown is designed for a combustion process with a gas flushed pilot chamber so that the ignition sparks impinge on the combustion chamber walls as late as possible.
B) Piston with trough-shaped piston crown. The piston crown is designed so that a turbulent flow generated on the inlet side is maintained.
C) Piston with omega piston crown recess. The piston crown is designed for optimal direct injection for diesel operation and is also used without changes for gas Otto engines for cost reasons and for the sake of simplicity. However, the latter is despite a possibly poorer combustion process.
D) Piston with pot piston crown recess. The piston crown is designed so that there is a squish flow in the radial direction between the piston edge and the cylinder head. Moreover, the rotational flow in the pot piston crown recess is boosted.
Pistons with pot piston crown recesses are very well suited to engines with rotational inlet channels and chamber plugs. During the compression stroke the mixture is displaced via the edge of the piston crown (squish edge) of the piston into the pot piston crown recess. During the expansion stroke the mixture is sucked back out of the pot piston crown recess. Said process leads to strong squish flows, especially near top dead centre.
In addition to the squish flow, the pot piston crown recess also leads to an acceleration of the rotational flow generated on the inlet side. Because of the conservation of angular momentum, the angular speed of the rotational flow increases if the mixture is displaced inwards into the pot piston crown recess.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.